Expandable structures for deployment in interior body regions

ABSTRACT

An expandable structure carried at the end of a catheter tube assembly can be contracted and/or wrapped to present a reduced profile during deployment and/or removal from a targeted tissue site.

RELATED APPLICATIONS

This application is a divisional of copending U.S. patent applicationSer. No. 10/784,392, filed Feb. 23, 2004, which is a divisional of U.S.patent application Ser. No. 09/595,963, filed Jun. 19, 2000 (now U.S.Pat. No. 6,719,773), which is a continuation-in-part of U.S. patentapplication Ser. No. 09/420,529, filed Oct. 19, 1999, and entitled“Expandable Preformed Structures for Deployment in Interior BodyRegions,” now U.S. Pat. No. 6,607,544, and which is also acontinuation-in-part of U.S. patent application Ser. No. 09/088,459,filed Jun. 1, 1998, and entitled “Expandable Preformed Structures forDeployment in Interior Body Regions,” now abandoned. This application isalso a continuation-in-part of U.S. patent application Ser. No.09/827,260, filed Apr. 5, 2001, and entitled Methods for TreatingFractured and/or Diseased Bone (now U.S. Pat. No. 6,726,691).

FIELD OF THE INVENTION

The invention relates to expandable structures, which, in use, aredeployed in interior body regions of humans and other animals.

BACKGROUND OF THE INVENTION

The deployment of expandable structures, sometimes generically called“balloons,” into cancellous bone is known. For example, U.S. Pat. Nos.4,969,888 and 5,108,404 disclose apparatus and methods using expandablestructures to compact cancellous bone for the fixation of fractures orother osteoporotic and non-osteoporotic conditions of human and animalbones.

In these and other clinical indications, it is desirable to use tissueinsertion and deployment tools that are small, so that access to thetargeted tissue site can be achieved using minimally invasiveprocedures. Still, it is also desirable to deploy structures that, inuse within the targeted tissue site, are capable of assuming enlarged,durable shapes, so that cortical bone can be displaced in a desiredmanner and/or large cavities can be created in cancellous bone withoutover-expansion, puncture, and/or abrasion of the structure.

There is a need to meet the demand for small insertion tools withoutconflicting with the objective to deploy large expandable structures.

SUMMARY OF THE INVENTION

The invention provides systems and methods that permit expandable,large, durable structures to be deployed through small, minimallyinvasive accesses.

One aspect of the invention provides systems and methods for treatingbone. The systems and methods establish a percutaneous access path to abone structure having cortical bone enclosing a cancellous bone volume.

The systems and methods deploy a structure into the bone structurethrough the percutaneous access path. The systems and methods move thestructure to a wrapped condition prior to passage and withdrawal of thestructure through the percutaneous access path. The systems and methodsexpand the structure to an expanded condition to form a cavity in thecancellous bone volume. The systems and methods convey a filler materialinto the cavity.

Features and advantages of the inventions are set forth in the followingDescription and Drawings, as well as in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a coronal view of a vertebral body;

FIG. 2 is a lateral view of the vertebral body shown in FIG. 1;

FIG. 3 is a plan view of a tool which carries at its distal end anexpandable structure that embodies features of the invention;

FIG. 4 is an enlarged view of the proximal end of the tool shown in FIG.3, showing the three part catheter tube assembly, stylet, and theirconnection to a handle;

FIG. 5 is an enlarged view of the distal end of the tool shown in FIG.3, showing the three part catheter tube assembly, stylet, and theirconnection to the expandable structure;

FIG. 6 is a further enlarged view of the distal end of the tool shown inFIG. 5, showing further details of the connection between the three partcatheter tube assembly, stylet, and expandable structure;

FIG. 7 is a further enlarged view of the proximal end of the tool shownin FIG. 4, showing further details of the connection between the threepart catheter tube assembly, stylet, and handle;

FIG. 8 is a sectional view of the three part catheter tube assembly andstylet taken generally along line 8-8 in FIG. 7;

FIG. 9 is a plan view of the tool shown in FIG. 3, with the expandablestructure in a partially twisted and wrapped condition caused byrotation of the stylet within the catheter tube assembly;

FIG. 10 is a plan view of the tool shown in FIG. 3, with the expandablestructure in a fully twisted and wrapped condition caused by rotation ofthe stylet within the catheter tube assembly;

FIG. 11 is a coronal view of the vertebral body shown in FIG. 1, withthe expandable structure of the tool shown in FIG. 3 placed in a fullywrapped, low profile condition, ready for deployment through a cannulainto the interior of the vertebral body;

FIG. 12 is a coronal view of the vertebral body shown in FIG. 11, withthe expandable structure of the tool shown in a fully deployed andexpanded condition to compress cancellous bone and form a cavity;

FIG. 13 is a coronal view of the vertebral body shown in FIG. 12, uponremoval of the tool, showing the cavity formed by the compression ofcancellous bone by the expandable structure;

FIG. 14 is a plan view of an alternative embodiment of a tool whichcarries at its distal end an expandable structure that embodies featuresof the invention;

FIG. 15 is a plan view of another alternative embodiment of a tool whichcarries at its distal end an expandable structure that embodies featuresof the invention;

FIG. 16 is a perspective view of an alternate embodiment of a tool whichcarries at its distal end an expandable structure that embodies featuresof the invention;

FIG. 17 is a perspective view of the tool of FIG. 16, with the toolinserted through a cannula;

FIG. 18 is a side plan view of a handle suitable for use with the toolof FIG. 16; and

FIG. 19 is a partial plan view of one embodiment of a strutincorporating features of the invention.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment describes improved systems and methods thatembody features of the invention in the context of treating bones. Thisis because the systems and methods can be advantageously applied forthis purpose. However, aspects of the invention can be advantageouslyapplied for diagnostic or therapeutic purposes in other areas of thebody.

The systems and methods will be more specifically described in thecontext of the treatment of human vertebra. Of course, other human oranimal bone types can be treated in the same or equivalent fashion. Byway of example, and not by limitation, the present systems and methodscould be used in any bone having bone marrow therein, including theradius, the humorous, the vertebrae, the femur, the tibia or thecalcaneus.

I. Anatomy of a Vertebral Body

FIG. 1 shows a coronal (top) view of a human lumbar vertebra 12. FIG. 2shows a lateral (side) view of the vertebra 12. The vertebra 12 includesa vertebral body 26, which extends on the anterior (i.e., front orchest) side of the vertebra 12. The vertebral body 26 is shapedgenerally like a hockey puck.

As FIGS. 1 and 2 show, the vertebral body 26 includes an exterior formedfrom compact cortical bone 28. The cortical bone 28 encloses an interiorvolume of reticulated cancellous, or spongy, bone 32 (also calledmedullary bone or trabecular bone).

The spinal canal 36 (see FIG. 1), is located on the posterior (i.e.,back) side of each vertebra 12. The spinal cord (not shown) passesthrough the spinal canal 36. The vertebral arch 40 surrounds the spinalcanal 36. Left and right pedicles 42 of the vertebral arch 40 adjoin thevertebral body 26. The spinous process 44 extends from the posterior ofthe vertebral arch 40, with the left and right transverse processes 46extending from the sides of the vertebral arch.

It may be indicated, due to disease or trauma, to compress cancellousbone within the vertebral body. The compression, for example, can beused to form an interior cavity, which receives a filling material,e.g., a flowable material that sets to a hardened condition, like bonecement, allograft tissue, autograft tissue, hydroxyapatite, or syntheticbone substitute, as well as a medication, or combinations thereof, toprovide improved interior support for cortical bone or other therapeuticfunctions, or both. The compaction of cancellous bone may also exertinterior force upon cortical bone, making it possible to elevate or pushbroken and compressed bone back to or near its original prefracture, orother desired, condition.

Alternatively, it may be indicated to move cortical bone, with orwithout concurrent compaction of cancellous bone. The present system andmethods can be utilized to directly and/or indirectly displace corticalbone in one or more desired directions.

II. Tool for Treating Vertebral Bodies

FIGS. 3 to 5 show a tool 48 for compacting cancellous bone, creating acavity within the bone and/or displacing cortical bone. The tool 48includes a catheter tube assembly 10 made, e.g., from metal or extrudedplastic materials. If desired, the catheter tube can be generallyflexible. The distal end of the catheter tube assembly 10 carries anexpandable structure 56, which is made, e.g., from a deformable plasticor metal material. Further details of the physical and mechanicalproperties of the material for the catheter tube assembly 10 andexpandable structure 56 will be described later. In use, the structure56 is deployed and expanded inside bone, e.g., in the vertebral body 26shown in FIGS. 1 and 2, to compact cancellous bone 32 and/or displacecortical bone, as will also be described later.

As best shown in FIGS. 4 and 5, the catheter tube assembly 10 includesan outer catheter body 16, a middle catheter body 20, and an innercatheter body 18. The middle catheter body 20 extends through the outercatheter body 16. The inner catheter body 18 extends through the middlecatheter body 20.

As best shown in FIG. 7, the proximal end of the middle catheter body 20is coupled to the proximal end of the outer catheter body 16. Thecoupled proximal ends of the outer and middle catheter bodies 16 and 20are, in turn, jointly coupled to the distal end of a luer fitting 22 ona y-shaped adapter 14, which serves as a handle for the tool 48.

As FIG. 7 also shows, the proximal end of the inner catheter body 18extends within the adapter 14 beyond the coupled proximal ends of theouter and middle catheter bodies 16 and 20. The extended proximal end ofthe inner catheter body 18 is coupled to the y-shaped handle adapter 14at a location proximal to an inflation port 38.

As FIG. 6 shows, the distal end of the inner catheter body 18 extendsbeyond the distal end of the middle catheter body 20. As FIG. 6 alsoshows, the expandable structure 56 is coupled at its distal end to thedistal end of the inner catheter body 18. The expandable structure 56 iscoupled at its proximal end to the distal end of the middle catheterbody 20. The distal end of the outer catheter body 16 is coupled to themiddle catheter body 20 adjacent to the junction of the expandablestructure 56 and the middle catheter body 20.

As FIG. 8 shows, the interior diameter of the middle catheter body 20 islarger than the exterior diameter of the inner catheter body 18. Aninterior passage 34 is thereby defined between them. In use, theinterior passage 34 conveys a pressurized flowable medium, e.g., sterilewater, radiopaque fluid (such as CONRAY™ solution, from Mallinkrodt,Inc.), gas, or other flowable substance into the structure 56, to expandit. The inflation port 38 on the handle 14 (see, e.g., FIG. 7) serves,in use, to couple the interior passage 34 to the source of pressurizedflowable medium (not shown).

The inner catheter body 18 itself defines an interior lumen 50 (see FIG.8) within the interior passage 34. A generally flexible, torquetransmitting stylet 52 made, e.g., from metal or plastic, extendsthrough the interior lumen 50. As FIG. 6 best shows, the distal end ofthe stylet 52 is jointly coupled with the distal end of the innercatheter body 18 to the distal end of the expandable structure 56.

As FIG. 7 shows, the proximal end of the stylet 52 is coupled to arotatable luer cap 24. The luer cap 24 rotates on threads 58 about theproximal luer fitting 30 on the y-shaped adapter/handle 14. Twisting theluer cap 24 on the threads 58 (arrow A in FIG. 4) rotates the stylet 52within the inner catheter body 18 (arrow B in FIG. 4). The proximal endsof the middle catheter body 20 and outer catheter body 16 desirablyremain substantially stationary, and do not rotate significantly withthe stylet 52.

The torque caused by twisting the luer cap 24 is transmitted by thestylet 52 to the distal ends of inner catheter body 18 and theexpandable structure 56, which, as before described, are jointly coupledto the distal end of the stylet 52. The proximal end of the expandablestructure 56, being coupled to the substantially stationary middlecatheter body 20, desirably remains stationary.

As the luer cap 54 is rotated in the direction of the threads 58 (whichis clockwise in the drawings, shown by arrow A in FIG. 9), the distalend of the expandable structure 56 rotates in the same direction (shownby arrow B in FIG. 9) while the proximal end of the expandable structure56 desirably remains substantially stationary.

It should be appreciated that the proximal end of the structure 56 neednot remain substantially stationary to accomplish one or more goals ofthe invention. Rather, it is the differential rotation of the proximaland distal ends of the structure 56 that desirably wraps the structure56 to some degree. For example, if the middle catheter body 20 and/orouter catheter body 16 deformed during rotation of the stylet 52,allowing the proximal end of the structure 56 to rotate, the differencesin rotation between the distal and proximal ends of the structure 56would still desirably “wrap” the structure 56 to some degree. In asimilar manner, if some portion of the structure were rotated relativeto another portion of the structure, and the distal and proximal ends ofthe structure remained substantially stationary relative to each other,the structure would still desirably “wrap” to some degree.

Similarly, if the stylet 52 were substantially motionless and theproximal end of the catheter tube assembly 10 were rotated, thestructure 56 would also “wrap.” Desirably, in this arrangement, theproximal end of the structure 56 will rotate at least one-third (⅓rd) ofa complete rotation relative to the distal end of the structure 56. Moredesirably, the proximal end of the structure 56 will rotate at least onecomplete rotation relative to the distal end of the structure. Even moredesirably, the proximal end of the structure will rotate at least twocomplete rotations relative to the distal end of the structure 56. Mostdesirably, the proximal end of the structure 56 will rotate at leastthree complete rotations relative to the distal end of the structure 56.

As FIGS. 9 and 10 show, the resulting rotational force transmitted bythe stylet 52 progressively twists the distal end of the structure 56relative to the proximal end of the structure 56. As FIGS. 9 and 10shows, the progressive twisting wraps the structure 56 inwardly aboutthe distal end of the inner catheter body 18. Desirably, this wrappingaction also distributes the structure uniformly around the innercatheter body.

As FIGS. 9 and 10 show, the wrapping progressively reduces the outsidediameter of the structure 56. When fully wrapped about the innercatheter body 18 (as FIG. 10 depicts), the outside diameter of thestructure 56 desirably approximates or is less than the inside diameterof the cannula 78 (see FIG. 11). Similarly, because the inner catheterbody 18 is secured to both the y-shaped adapter 14 and the distal end ofthe stylet 52, the rotation of the stylet 52 will also desirably “twist”the inner catheter body 18, desirably reducing the outside diameter ofthe inner catheter body 18 and further reducing the overall outsidediameter of the structure 56.

The threads 58 desirably impose a frictional drag, which resists thecounter resilience of the material of the structure 56 tending to unwrapthe wrapped structure 56. The frictional drag keeps the structure 56within a range of wrapped conditions (see FIG. 9) in the absence ofrotational force applied to the luer cap 24. Of course, other devices,such as magnetic or frictional locks or detent mechanisms, could be usedto secure the structure 56 in a wrapped, partially-wrapped and/orunwrapped condition.

In the disclosed embodiment, the movement of the luer cap 24 along thelongitudinal axis L of the tool 48, also longitudinally stretches and/orradially shrinks the structure 56, further reducing the overall outsidediameter. For example, as the luer cap 24 rotates clockwise, the luercap 24 moves toward the distal luer fitting 22 along the longitudinalaxis L. The stylet 52, which is secured to the luer cap 24, is similarlydisplaced along the longitudinal axis L, which in turn displaces thedistal end of the expandable structure 56. This displacement increasesthe longitudinal length of the structure 56, which “stretches” theexpandable structure 56, further drawing the structure 56 against theinner catheter body 18 and/or causing a thinning of the structure 56.This also desirably reduces the outside diameter of the structure 56.

If desired, the threads can be reversed, such that clockwise rotation ofthe luer cap 24 causes the luer cap 24 to move away from the distal luerfitting 22. In this alternative arrangement, clockwise rotation of theluer cap 24 would allow the longitudinal length of the structure toshorten as it wraps about the inner catheter body 18.

Rotation of the luer cap 24 in the opposite direction, which iscounterclockwise in the drawings, causes the structure 56 to unwrap fromabout the inner catheter body 18, returning to its normal outsidediameter for use (as shown in FIG. 3).

The tool 48 can also include an insertion sleeve 54 (see FIG. 3). Theinsertion sleeve 54 desirably slides along the outer catheter body 16.The insertion sleeve 54 can be slid forward over the wrapped structure56, to protect the structure 56 and/or aid insertion of the structure 56into a cannula 78. Once the structure 56 is deployed into the cannula78, the insertion sleeve 54 can be slid aft away from the structure 56,and can, if desired, engage the handle 14 during further use of the tool48.

FIG. 14 shows an alternative embodiment of a tool 48A for compactingcancellous bone, creating a cavity within bone and/or displacingcortical bone, which embodies features of the invention. Because manystructural components of the tool 48A are similar to those of the tool48, like reference numerals will be used to identify like components.

In this embodiment, the proximal ends of the outer, middle, and innercatheter bodies 16, 20, and 18 are coupled to a t-shaped adapter 100.The proximal end of the stylet 52 is coupled to a luer cap 106.Desirably, the luer cap 106 will be spaced apart from a correspondingluer fitting 104 when the structure 56 is unstretched and/or untwisted.In the disclosed embodiment, the luer cap 106 is spaced approximatelyone-fourth (¼th) inches from the luer fitting 104, although this spacingcould be increased or decreased, depending upon the length of the stylet52 and the amount of stretching desired for the structure 56.

When the tool 48A is prepared for deployment, the luer cap 106 isdesirably pushed longitudinally towards the luer fitting 104 so that itcontacts the luer fitting 104. This desirably elongates the structure 56and reduces its overall outside diameter. The luer cap 106 is thenengaged with the luer fitting 104. If desired, the luer cap 106 and luerfitting 106 can engage by twisting, which will twist the structure andfurther reduce the overall outside diameter. Alternatively, the luer cap106 and luer fitting could be a snap-lock type fitting.

FIG. 15 shows another alternative embodiment of a tool 48B forcompacting cancellous bone, creating a cavity within bone and/ordisplacing cortical bone, which embodies features of the invention. Asin FIG. 14, because many of the structural components of the tool 48Bare similar to those of the tool 48, like reference numerals will beused to identify like components.

In this embodiment, the proximal ends of the outer, middle and innercatheter bodies 16, 20 and 18 are coupled to a t-shaped adapter 100. Thet-shaped adapter 100 comprises a stationary fitting 109, a rotatablefitting 113, and an automatic or manually operated detent mechanism 107.One or more notches 111 are disposed on the stationary fitting 109. Theproximal end of the stylet 52 is desirably coupled to the rotatablefitting 113.

When the tool 48B is prepared for deployment, the detent mechanism 107can be disengaged from the one or more notches 111, and the rotatablefitting 113 rotated, which desirably twists the structure 56 and reducesits overall outside diameter. The detent mechanism 107 is then engagedto secure the structure 56 in its low profile position for insertioninto the cannula. If desired, the detent mechanism 107 can incorporatethreads or other devices which advance/withdraw the stylet 52 inresponse to rotation of the rotatable fitting.

Various materials can be selected for the component parts of the tool48. Furthermore, the dimensions of the component parts of the tool 48can also vary, according to its intended use. The following table listspreferred component materials and dimensions, which are well suited fora tool 48 that can be deployed for use in a vertebral body:

Component Material Dimension (Inches) Outer catheter body TEXIN ® 5270Outside Diameter: 0.124 16 Polyurethane Inside Diameter: 0.102 MiddleCatheter body TEXIN ® 5270 Outside Diameter: 0.078 20 PolyurethaneInside Diameter 0.054 Inner Catheter Body TEXIN ® 5270 Outside Diameter0.035 18 Polyurethane Inside diameter: 0.025 Expandable StructureTEXIN ® 5286 Polyurethane As formed: Axial Length (from distal end ofmiddle catheter tube to distal end of inner catheter tube): 0.949Wrapped Diameter: 0.124 Normal Non-Expanded Diameter: 0.270 Tool Totalend to end length: 15.75 Stylet Stainless Steel Outside Diameter: 0.023Insertion Sleeve 54 PEBAX ® Tubing Outside Diameter: 0.172″ InsideDiameter: 0.140 Length: 1.5The component parts of the tool 48 can be formed and assembled invarious ways. A preferred assembly will now be described.

A. The Expandable Structure

The material from which the structure 56 is made should possess variousphysical and mechanical properties to optimize its functionalcapabilities to compact cancellous bone. Important properties for thestructure include one or more of the following: (1) the ability toexpand in volume; (2) the ability to deform in a desired way whenexpanding and assume a desired shape inside bone; and/or (3) the abilityto withstand abrasion, tearing, and puncture when in contact withcancellous and/or cortical bone.

1. Expansion Property

A first desired property for the structure material is the ability toexpand or otherwise increase in volume without failure. This propertyenables the structure 56 to be deployed in a collapsed, low profilecondition subcutaneously, e.g., through a cannula, into the targetedbone region. This property also enables the expansion of the structure56 inside the targeted bone region to press against and compresssurrounding cancellous bone, or move cortical bone to a prefracture orother desired condition, or both.

The desired expansion property for the structure material can becharacterized in one way by ultimate elongation properties, whichindicate the degree of expansion that the material can accommodate priorto failure. Sufficient ultimate elongation permits the structure 56 tocompact cortical bone, as well as lift contiguous cortical bone, ifnecessary, prior to wall failure. Desirably, the structure 56 willcomprise material able to undergo an ultimate elongation of at least50%, prior to wall failure, when expanded outside of bone. Moredesirably, the structure will comprise material able to undergo anultimate elongation of at least 150%, prior to wall failure, whenexpanded outside of bone. Most desirably, the structure will comprisematerial able to undergo an ultimate elongation of at least 300%, priorto wall failure, when expanded outside of bone.

Alternatively, the structure material can comprise one or morenon-compliant or partially compliant materials having substantiallylower ultimate elongation properties, including, but not limited to,kevlar, aluminum, nylon, polyethylene, polyethyiene-terephthalate (PET)or mylar. Such a structure would desirably be initially formed to adesired shape and volume, and then contracted to a collapsed, lowprofile condition for introduction through a cannula into the targetedbone region. The structure could then be expanded to the desired shapeand volume to press against and compress surrounding cancellous boneand/or move cortical bone to a prefracture or desired condition, orboth. As another alternative, the structure could comprise a combinationof non-compliant, partially compliant and/or compliant materials.

2. Shape Property

A second desired property for the material of the structure 56, eitheralone or in combination with the other described properties, is theability to predictably deform during expansion, so that the structure 56consistently achieves a desired shape inside bone.

The shape of the structure 56, when expanded in bone, is desirablyselected by the physician, taking into account the morphology andgeometry of the site to be treated. The shape of the cancellous bone tobe compressed and/or cortical bone to be displaced, and the localstructures that could be harmed if bone were moved inappropriately, aregenerally understood by medical professionals using textbooks of humanskeletal anatomy along with their knowledge of the site and its diseaseor injury, and also taking into account the teachings of U.S. patentapplication Ser. No. 08/788,786, filed Jan. 23, 1997, and entitled“Improved Inflatable Device for Use in Surgical Protocol Relating toFixation of Bone,” which is incorporated herein by reference. Thephysician is also desirably able to select the desired expanded shapeinside bone based upon prior analysis of the morphology of the targetedbone using, for example, plain film x-ray, fluoroscopic x-ray, or MRI orCT scanning.

Where compression of cancellous bone and/or cavity creation is desired,the expanded shape inside bone is selected to optimize the formation ofa cavity that, when filled with a selected material, provides supportacross the region of the bone being treated. The selected expanded shapeis made by evaluation of the predicted deformation that will occur withincreased volume due to the shape and physiology of the targeted boneregion.

Where displacement of cortical bone is desired, the expanded shape canbe selected to optimize displacement of the cortical bone in the desireddirection(s), as well as to distribute forces in a desired manner acrossthe targeted cortical bone region. If desired, the structure can bedesigned to distribute forces evenly and/or uniformly across thetargeted cortical bone region. Alternatively, the structure can bedesigned to impart a maximum force on a specific area of the corticalbone so as to cause desired fracture and/or maximum displacement ofspecific cortical bone regions.

In some instances, it is desirable, when creating a cavity, to also moveor displace the cortical bone to achieve the desired therapeutic result.Such movement is not per se harmful, as that term is used in thisSpecification, because it is indicated to achieve the desiredtherapeutic result. By definition, harm results when expansion of thestructure 56 results in a worsening of the overall condition of the boneand surrounding anatomic structures, for example, by injury tosurrounding tissue or causing a permanent adverse change in bonebiomechanics.

As one general consideration, in cases where the bone disease causingfracture (or the risk of fracture) is the loss of cancellous bone mass(as in osteoporosis), the selection of the expanded shape of thestructure 56 inside bone should take into account the cancellous bonevolume which should be compacted to achieve the desired therapeuticresult. An exemplary range is about 30% to 90% of the cancellous bonevolume, but the range can vary depending upon the targeted bone region.Generally speaking, compacting less of the cancellous bone volume leavesmore uncompacted, diseased cancellous bone at the treatment site.

Another general guideline for the selection of the expanded shape of thestructure 56 inside bone is the amount that the targeted fractured boneregion has been displaced or depressed. The expansion of the structure56 inside a bone can elevate or push the fractured cortical wall back toor near its anatomic position occupied before fracture occurred.

For practical reasons, it is often desired that the expanded shape ofthe structure 56 inside bone, when in contact with cancellous bone,substantially conforms to the shape of the structure 56 outside bone,when in an open air environment. This allows the physician to select inan open air environment a structure having an expanded shape desired tomeet the targeted therapeutic result, with the confidence that theexpanded shape inside bone will be similar in important respects.

An optimal degree of shaping can be achieved by material selection andby special manufacturing techniques, e.g., thermoforming or blowmolding, as will be described in greater detail later.

In some instances, it may not be necessary or desired for the structureto predictably deform and/or assume a desired shape during expansioninside bone. Rather, it may be preferred that the structure expand in asubstantially uncontrolled manner, rather than being constrained in itsexpansion. For example, where compaction of weaker sections of thecancellous bone is desired, it may be preferred that the structureinitially expand towards weaker areas within the bone. In such cases,the structure can be formed without the previously-described shapeand/or size, and the expanded shape and/or size of the structure can bepredominantly determined by the morphology and geometry of the treatedbone.

3. Toughness Property

A third desired property for the structure 56, either alone or incombination with one or more of the other described properties, is theability to resist surface abrasion, tearing, and puncture when incontact with cancellous bone. This property can be characterized invarious ways.

One way of measuring a material's resistance to abrasion, tearing and/orpuncture is by a Taber Abrasion test. A Taber Abrasion test evaluatesthe resistance of a material to abrasive wear. For example, in a TaberAbrasion test configured with an H-18 abrasive wheel and a 1 kg load for1000 cycles (ASTM Test Method D 3489), Texin® 5270 material exhibits aTaber Abrasion value of approximately 75 mg loss. As another example,under the same conditions Texin® 5286 material exhibits a Taber Abrasionvalue of approximately 30 mg loss. Typically, a lower Taber Abrasionvalue indicates a greater resistance to abrasion. Desirably, oneembodiment of the structure will comprise material having a TaberAbrasion value under these conditions of less than approximately 200 mgloss. More desirably, the structure will comprise material having aTaber Abrasion value under these conditions of less than approximately145 mg loss. Most desirably, the structure will comprise material havinga Taber Abrasion value under these conditions of less than approximately90 mg loss. Of course, materials having a Taber Abrasion value ofgreater than or equal to 200 mg loss may be utilized to accomplish someor all of the objectives of the present invention.

Another way of measuring a material's resistance to abrasion, tearingand/or puncture is by Elmendorf Tear Strength. For example, under ASTMTest Method D 624, Texin® 5270 material exhibits a Tear Strength of1,100 lb-ft/in. As another example, under the same conditions, Texin®5286 exhibits a Tear Strength of 500 lb-ft/in. Typically, a higher TearStrength indicates a greater resistance to tearing. Desirably, analternate embodiment of the structure will comprise material having aTear Strength under these conditions of at least approximately 150lb-ft/in. More desirably, the structure will comprise material having aTear Strength under these conditions of at least approximately 220lb-ft/in. Most desirably, the structure will comprise material having aTear Strength under these conditions of at least approximately 280lb-ft/in. Of course, materials having a Tear Strength of less than orequal to 150 lb-ft/in may be utilized to accomplish some or all of theobjectives of the present invention.

Another way of measuring a material's resistance to abrasion, tearingand/or puncture is by Shore Hardness. For example, under ASTM TestMethod D 2240, Texin® 5270 material exhibits a Shore Hardness of 70D. Asanother example, under the same conditions, Texin® 5286 materialexhibits a Shore Hardness of 86A. Typically, a lower Shore Hardnessnumber on a given scale indicates a greater degree of elasticity,flexibility and ductility. Desirably, another alternate embodiment ofthe structure will comprise material having a Shore Hardness under theseconditions of less than approximately 75D. More desirably, the structurewill comprise material having a Shore Hardness under these conditions ofless than approximately 65D. Most desirably, the structure will comprisematerial having a Shore Hardness under these conditions of less thanapproximately 100A. Of course, materials having a Shore Hardness ofgreater than or equal to 75D may be utilized to accomplish some or allof the objectives of the present invention.

It should also be noted that another alternate embodiment of a structureincorporating a plurality of materials, such as layered materials and/orcomposites, may possess significant resistance to surface abrasion,tearing and puncture. For example, a layered expandable structureincorporating an inner body formed of material having a Taber Abrasionvalue of greater than 200 mg loss and an outer body having a shorehardness of greater than 75D might possess significant resistance tosurface abrasion, tearing and puncture. Similarly, other combinations ofmaterials could possess the desired toughness to accomplish the desiredgoal of compressing cancellous bone and/or moving cortical bone prior tomaterial failure.

4. Creating a Pre-Formed Structure

The expansion and shape properties just described can be enhanced andfurther optimized for compacting cancellous bone by selecting anelastomer material, which also possess the capability of beingpreformed, i.e., to acquire a desired shape by exposure, e.g., to heatand pressure, e.g., through the use of conventional thermoforming orblow molding techniques. Candidate materials that meet this criteriainclude polyurethane, silicone, thermoplastic rubber, nylon, andthermoplastic elastomer materials.

As described earlier, in the illustrated embodiment, TEXIN® 5286polyurethane material is used. This material is commercially availablefrom Bayer in pellet form. The pellets can be processed and extruded ina tubular shape.

The tubular extrusion can then be cut into individual lengths forfurther processing. The structure 56 can be formed by exposing a cuttube length to heat and then enclosing the heated tube 60 within a moldwhile positive interior pressure is applied to the tube length, as iswell known in the art.

Further details of the manufacture of a structure suitable for use withthe present invention can be found in U.S. patent application Ser. No.09/420,529, filed Oct. 19, 1999, and entitled “Expandable PreformedStructures for Deployment in Interior Body Regions,” which isincorporated herein by reference.

B. Assembly of the Tool

The outer catheter body 16, middle catheter body 20, and inner catheterbody 18 can each comprise extruded tubing made, e.g., from TEXIN® 5270Material. The TEXIN® material can be purchased in pellet form fromBayer. The catheter bodies 16, 18, and 20 can be extruded in a tubularshape. Representative process settings for the extrusions can be foundin U.S. patent application Ser. No. 09/420,529, filed Oct. 19, 1999, andentitled “Expandable Preformed Structures for Deployment in InteriorBody Regions,” which is incorporated herein by reference.

In assembling the tool 48, the proximal end of the structure 56 isbonded to the distal end of the middle catheter body 20 (as FIG. 6shows) through heat bonding or the use of a suitable adhesive. Themiddle catheter body 20 and outer catheter body 16 are cut to a desiredfinal length, e.g., which in a representative embodiment isapproximately 350 mm measured from the center of the structure 56. Theouter catheter body 16 is slid over the middle catheter body 20, fromthe proximal end toward the distal end. The proximal and distal ends ofthe catheter bodies 16 and 20 are then bonded together (as FIG. 7shows).

A suitable UV adhesive (e.g., Dymax 204 CTH, available commercially fromDymax Corp) is applied to the joined proximal ends of the outer catheterbody 16 and middle catheter body 20. The joined ends are inserted intothe luer fitting 22 of the handle 14 (as FIG. 7 shows). The adhesivejoint is cured, e.g., under UV light for an appropriate time period,e.g., 15 seconds. This secures the outer catheter body 16 and middlecatheter body 20 to the handle 14.

The distal end of the inner catheter body 18 is flared slightly (as FIG.6 shows), using, e.g., a 0.075″ flare tool. The inner catheter body 18is inserted, proximal end first, through the distal end of the structure56. The inner catheter body passes through the middle catheter body 20and into the luer fitting 30 on the y-shaped adapter/handle 14 (as FIG.7 shows).

The flared distal end of the inner catheter body 18 is heat bonded tothe distal end of the structure 56 (as FIG. 6 shows). The flare tool isdesirably kept in place during the heat bonding process, to preventcollapse of the flared distal end.

The proximal end of the inner catheter body 18 is cut to size, ifnecessary, and is secured to the luer fitting 30 using adhesive (as FIG.7 shows).

In one embodiment, the distal end of the stylet 52 is bent into a hookshape 60 (see FIG. 6). The unbent proximal end of the stylet 52 ispassed through the flared distal end of the inner catheter body 18,until the bent distal end 60 occupies the flared distal end. An adhesiveis applied into the flared distal end of the inner catheter body 18. Theadhesive closes the distal end of the inner catheter body 18 and bondsthe bent distal end 60 of the stylet 52 to the distal end of the innercatheter body 18, which is itself bonded to the distal end of thestructure 56. Alternatively, the distal end of the inner catheter body18 could be heat bonded to the hook shaped end 60 of the stylet 52.

The proximal end of the stylet 52, which extends outside the proximalend of the fitting 30, is cut to size and also bent into a hook shape 62(see FIG. 7). The bent proximal end 62 is bonded to the luer cap 24 byadhesive (see FIG. 7).

This completes the assembly of the tool 48. The tool 48 can then bepackaged for sterilization in a suitable kit.

If desired, the middle and outer catheter bodies 20 and 16 couldcomprise a single catheter body having sufficient torsional strength toaccomplish the objectives of the present invention. For example, theproximal end of the structure 56 and the distal end of the luer fitting22 could be secured to a hollow hypodermic tube of sufficient diameterto accommodate the inner catheter body 18 and stylet 52. Such a catheterbody, comprised of a medical material such as stainless steel orplastic, would have sufficient rigidity to withstand the torsionalforces described herein and accomplish the objectives of the presentinvention.

In another alternative embodiment, the middle and outer catheter bodies20 and 16 can be designed to deform and/or fail at or below thetorsional failure point of the structure 56. For example, where thestructure 56 can withstand a torsional force of at least ten ft-lbsbefore failure, the middle and outer catheter bodies 20 and 16 can bedesigned to together withstand a maximum of ten ft-lbs beforeexperiencing significant deformation and/or failure. By designing thecatheter bodies to deform and/or fail before the structure, thepotential for a complete radial tear and/or fragmentation of thestructure is significantly reduced and/or eliminated. Moreover, evenwhen the middle and outer catheter bodies 20 and 16 completely fail andseparate, the tool 48 retains significant structural integrity to besafely withdrawn from the patient.

Representative other details for the assembly of the catheter bodies 16,18, and 20, the stylet 52, and the handle 14 can be found in U.S. patentapplication Ser. No. 09/420,529, filed Oct. 19, 1999, and entitled“Expandable Preformed Structures for Deployment in Interior BodyRegions,” which is incorporated herein by reference.

III. Use of the Tool

A. Deployment in a Vertebral Body

The structure 56 is well suited for insertion into bone in accordancewith the teachings of U.S. Pat. Nos. 4,969,888, 5,108,404, 5,827,289,and 5,972,015, which are incorporated herein by reference.

For example, as FIG. 11 shows, access can be accomplished by drilling anaccess portal 76 through a side of the vertebral body 26 and partiallyinto cancellous bone inside the vertebral body 26. This is called alateral approach. Alternatively, the access portal can pass througheither pedicle 42, which is called a transpedicular approach, or canalong the anterior side of the vertebra. A hand held tool can be used tofacilitate formation of the access portal 76, such as disclosed incopending U.S. patent application Ser. No. 09/421,635, filed Oct. 19,1999, and entitled “Hand Held Instruments that Access Interior BodyRegions.” Another hand held tool that can be used to form the accessportal 76 and gain access is disclosed in copending U.S. patentapplication Ser. No. 09/014,229 filed Jan. 27, 1998 and entitled “ASlip-Fit Handle for Hand-Held Instruments that Access Interior BodyRegions.”

A guide sheath or cannula 78 is placed into communication with theaccess portal 76, which can comprise a component part of the hand heldtool just described.

Before advancement through the cannula 78, the luer cap 24 is rotated,as previously described, to wrap the structure 56 about the distal endof the inner catheter body 18 and stylet 52, as FIG. 11 shows.

The wrapping efficiently “packs” the structure 56 into a cylindricalshape, to significantly reduce the cross-sectional profile of thestructure 56 during its insertion through the cannula 78. Moreover, thewrapping uniformly-distributes the structure 56 about the inner catheterbody 18. Structures 56 having desired enlarged external diameters toachieve greater compaction of cancellous bone, can, before deploymentinto bone, be twisted down to significantly smaller external diametersfor deployment into bone through smaller diameter cannulas. This, inturn, enables smaller incisions and less invasive procedures.

Once the structure 56 has been twisted in one direction, e.g.,clockwise, for passage through the cannula 76 (by rotation of the luercap 24), the physician can chose to twist the entire catheter tubeassembly 10 as it advances through the cannula 78 in the oppositedirection, i.e., counterclockwise, which will desirably further reducethe profile of the structure 56.

Moreover, because the material of the structure 56 is twisted againstthe inner catheter body 18 and stylet 52, the normal force exerted bythe walls of the cannula 78 against the structure 56 is reduced.Accordingly, the low profile offers clearance between the structure 56and the cannula walls and desirably reduces the overall frictional dragon the structure. The twisted structure 56 passes readily through thecannula 78, without back pressure. Material wear or damage to thestructure 56 caused by frictional forces can also be minimized.

In addition to reducing the profile of the structure 56 for insertionthrough the cannula 78, the resultant twisting of the structure 56 alsoevenly tightens or “packs” the structure material against the innercatheter body 18 and stylet 52. This overall tightening of materialsignificantly reduces, and can essentially eliminate, the possibilitythat the material of the structure 56 can slide or “bunch-up” as thestructure 56 travels down the cannula 76. This outcome further reducesthe frictional forces associated with passage of the structure 56through the cannula 76 and/or the potential for damage to the structure56 occasioned by the passage.

The presence of the stylet 52 and the middle catheter body 20 also addssignificant torsional rigidity to the catheter tube assembly 10 of thetool 48. The increased torsional rigidity enables the physician toincrease the twisting pressure that can be imparted to the tool 48during insertion into and removal from the targeted interior boneregion. For example, if the structure 56 meets an obstruction duringdeployment or removal, the increased torsional rigidity, column strengthand yield strength of the catheter tube assembly 10 permits thephysician to twist and/or push and/or pull the structure 56 past theobstruction and/or move the obstruction.

Furthermore, the presence of the bent distal end 62 of the stylet 52 atthe distal end of the inner catheter tube 18 enhances the torsionalstrength of the bond between the catheter tube assembly 10 and thestructure 56. This can significantly increase the amount of torque thatcan be transmitted by the luer cap 24 via the stylet 52 to twist thedistal end of the structure 56. The twisting of the structure 56 itselfimparts significantly more rigidity to the distal end of the cathetertube assembly 10. This allows the physician to use the twisted structure56 itself to push or pull aside obstructions.

The presence of the stylet 52 also further facilitates passage of thestructure 56 through the cannula 78 by “pushing” the distal end of thestructure through the cannula 78 and the cancellous bone 32. Because thestylet has significant column strength, as the physician “pushes” thetool 48 through the cannula 78, this axial force is transmitted throughthe stylet 52 to the closed distal end of the structure 56. Theremainder of the structure 56 is then essentially “pulled” behind thedistal end. If the structure becomes wedged or caught within the cannula78, the “pulling” action of the distal end will typically cause thestructure 56 to extend longitudinally, thinning the structure 56 anddesirably freeing the obstruction.

As FIG. 11 shows, the catheter tube assembly 10 is advanced through thecannula 78 with the structure 56 wrapped in a low profile condition. Thestructure 56 is deployed into contact with cancellous bone 32 inside thevertebral body 12. Access in this fashion can be accomplished using aclosed, minimally invasive procedure or with an open procedure.

Once deployed inside bone, the luer cap 24 can be rotated in an oppositedirection to unwrap the structure 56 for use. As FIG. 12 shows,subsequent expansion of the structure 56 (indicated by arrows in FIG.12) compresses cancellous bone 32 in the vertebral body 26. Thecompression forms an interior cavity 80 in the cancellous bone 32. Aspreviously noted, the structure can alternatively be used to displacecortical bone directly, with or without concurrent compression ofcancellous bone.

After the cavity 80 is formed in the vertebral body and/or cortical boneis displaced to a desired position, it is also desirable to reduce thesize of the structure 56 so that it can be withdrawn from the vertebralbody 12. In prior arrangements, the physician releases the pressure ofthe inflation fluid and draws a suction on the structure 56, trying toreduce the cross sectional profile as much as possible to facilitateremoval through the cannula 78. However, should the structure 56, duringuse, develop pinhole leaks or tears or otherwise experience damage, itcan be difficult to draw and/or maintain a vacuum within the structure56, as bodily fluids or air can enter the compromised structure 56.

The ability to mechanically impart a low profile after use, by twistingthe structure 56, allows the profile of even a compromised structure 56to be reduced for removal through the cannula 78. Size reduction bytwisting can even obviate the absolute need for a strong vacuum,although it should be realized that the most efficient size reduction isideally achieved when a vacuum is drawn and the structure 56 is thentwisted.

Furthermore, expansion of the collapsed size of the structure 56,occasioned by plastic deformation and/or stretching of the structurematerial during cavity formation, can be accommodated by twisting theextra, stretched material up against the inner catheter body 18. In thismanner, all material will be desirably wrapped against the innercatheter body 18, preventing the structure 56 from “bunching up,” whichcan inhibit withdrawal of the catheter tube assembly 10.

Since both the inner catheter body 18 and the stylet 52 are attacheddirectly to the distal bond of the structure 56, the overall pullstrength of the catheter tube assembly 10 is also increased. The pullstrength is further enhanced by the presence of the bent end 62 of thestylet 52 bonded within the distal bond of the structure 56. Thisfurther increases the magnitude of the force a physician can use to pullthe structure 56 out of the vertebral body. Even if a complete failureof the bond occurs during use at the proximal end of the structure 56,or even if the structure 56 experiences a complete radial tear duringuse, the presence of the enhanced bond at the distal end of thestructure 56 makes it still possible to retrieve the entire damagedstructure 56 by pulling on the catheter tube assembly 10.

FIG. 16 depicts an alternate embodiment of a catheter tube assembly 400constructed in accordance with the teachings of the present invention.Because many of the features in this embodiment are similar tocomponents previously described, like reference numerals will be used todescribe similar components.

Catheter tube assembly 400 comprises an outer catheter body 16A, aninner catheter tube 18A and a stylet 52A which extends through the outerand inner catheter bodies. The proximal end of an expandable structure56A is attached to the distal end of the outer catheter body 16A, andthe distal end of the expandable structure 56A is secured to the distalend of the inner catheter tube 18A and stylet 52A. The proximal end ofthe stylet 52A is desirably attached to a cap 24A. One or more struts405, extending along the outer catheter body 16A, are attached at aproximal end to the cap 24A. A handle 410 is secured to the proximal endof the outer catheter body 16A. The proximal end of the inner cathetertube 18A is desirably secured within the handle 410 at a locationproximal to an inflation port 38A.

Desirably, the inner catheter tube 18A and stylet 52A are slidablerelative to the outer catheter body 16A.

Because the ends of the structure 56 are bonded to the inner cathetertube/stylet and the outer catheter tube, however, longitudinaldisplacement of the stylet 52A and inner catheter tube 18A will causethe structure 56A to stretch or contract. When the handle 410 is drawntowards the cap 24A, therefore, the outer catheter body 16A slides alongthe inner catheter body/stylet and draws the proximal end of thestructure 56A towards the cap 24A, which stretches the structure 56Alongitudinally, reducing its outer profile. When the handle 410 isreleased, the structure will typically attempt to regain its originalshape, thereby drawing the handle 410 away from the cap 24A towards itsoriginal resting position.

In use, the physician is able to use a single hand to draw the handle410 towards the cap 24A, reducing the outer profile of the structure 56for insertion through a cannula 78. The structure is then advancedthrough the cannula 78 in this reduced profile condition. Once thestructure 56 enters the vertebral body, the handle 410 may be released,allowing the structure 56 to assume its original shape. The structurecan then be utilized as previously described.

It should be understood that varying degrees of force may be imparted tothe handle 410 to extend the structure 56 to a desired degree. Forexample, in the disclosed embodiment, a force of 4 ounces will extendthe structure approximately 3/16″. Similarly, a force of 3 pounds willextend the structure approximately ½″. Desirably, a force of at leastapproximately ½ ounce will extend the structure to a useful degree. Moredesirably, a force of at least approximately 2 ounces will extend thestructure to a useful degree. Even more desirably, a force of at leastapproximately 8 ounces will extend the structure to a useful degree.Most desirably, a force of at least approximately 1 pound will extendthe structure to a useful degree.

The disclosed embodiment further includes a stop which inhibits and/orprevents the assembly 400 from advancing beyond a predetermined distanceinto the vertebral body (not shown). In this embodiment, as the assembly400 is advanced to a desired position within the vertebral body, thedistal ends of the struts 405 will desirably contact one or more contactsurfaces 420 on the cannula 78, thereby preventing further advancementof the assembly 400 through the cannula 78. (See FIG. 17.) Because thestruts 405 are connected to the stylet 52A, and the stylet 52A extendsto the distal end of the structure 56, the maximum penetration depth ofthe assembly 400 can be controlled. Even where the profile of thestructure 56 has been reduced, the struts 405 will prevent the distaltip of the stylet 52A from advanced further than a predetermined depth.

If deeper penetration of the vertebral body is desired, the struts 405may be shortened by the physician, permitting the assembly 400 to extendfurther into the vertebral body. To facilitate such alterations, thestruts 405 can comprise one or more ridges, notches or grooves 425 atpredetermined locations, creating desired fracture lines along the strut405 and allowing the physician to quickly and easily shorten the struts405 to a desired length using appropriate tools such as surgicalscissors, clamps and/or various other types of cutting tools.

As FIG. 13 shows, subsequent collapse and removal of the structure 56leaves the cavity 80 in a condition to receive a filling material 88,e.g., bone cement, allograft tissue, autograft tissue, hydroxyapatite,granular bone material such as ProOsteon™, demineralized bone matrixsuch as Grafton™ or SRS™ calcium phosphate cement, Collagraft™ orsynthetic bone substitute. Alternatively, the material could comprise acompression-resistant material such as rubber, polyurethane,cyanoacrylate, silicone rubber, or metal. The material could alsocomprise a semi-solid slurry material (e.g., a bone slurry in a salinebase). Alternatively, the material could comprise stents, reinforcingbar (Re-Bar) or other types of internal support structures, whichdesirably resist compressive forces acting on the bone and/or fillermaterial. The material 88 desirably provides improved interiorstructural support for cortical bone 32.

The filling material may also comprise a medication, or a combination ofmedication and a compression-resistant material, as described above.Alternatively, the material can comprise a bone filling material whichdoes not withstand tensile, torsional and/or compressive forces withinthe cavity. For example, where the patient is not expected to experiencesignificant forces within the spine immediately after surgery, such aswhere the patient is confined to bed rest or wears a brace, the fillingmaterial need not be able to immediately bear tensile, torsional and/orcompressive loads. Rather, the filling material could provide a scaffoldfor bone growth, or could comprise a material which facilitates oraccelerates bone growth, allowing the bone to heal over a period oftime. As another alternative, the filling material could comprise aresorbable or partially-resorbable source of organic or inorganicmaterial for treatment of various bone or non-bone-related disordersincluding, but not limited to, osteoporosis, cancer, degenerative diskdisease, heart disease, acquired immune deficiency syndrome (AIDS) ordiabetes. In this way, the cavity and/or filler material could comprisea source of material for treatment of disorders located outside thetreated bone.

The compaction of cancellous bone 32, as shown in FIG. 12, can alsoexert an interior force upon the surrounding cortical bone 28. Theinterior force can elevate or push broken and compressed bone back to ornear its original prefracture, or other desired, condition. In the caseof a vertebral body 26, deterioration of cancellous bone 32 can causethe top and bottom plates (designated TP and BP in FIG. 2), as well asthe side walls (designated AW and PW in FIG. 2), to compress, crack, ormove closer together, reducing the normal physiological distance betweensome or all of the plates. In this circumstance, the interior forceexerted by the structure 56 as it compacts cancellous bone 32 moves someor all of the plates and/or walls farther apart, to thereby restore someor all of the spacing between them, which is at or close to the normalphysiological distance. As previously described, the structure canalternately be used to directly displace cortical bone, with or withoutconcurrent compaction of cancellous bone.

There are times when a lesser amount of cancellous bone compaction isindicated. For example, when the bone disease being treated islocalized, such as in avascular necrosis, or where local loss of bloodsupply is killing bone in a limited area, an expandable structure 56 cancompact a smaller volume of total bone. This is because the diseasedarea requiring treatment is smaller.

Another exception lies in the use of an expandable structure 56 toimprove insertion of solid materials in defined shapes, likehydroxyapatite and components in total joint replacement. In thesecases, the structure shape and size is defined by the shape and size ofthe material being inserted.

Yet another exception lies in the use of expandable structures in bonesto create cavities to aid in the delivery of therapeutic substances, asdisclosed in copending U.S. patent application Ser. No. 08/485,394,previously mentioned. In this case, the cancellous bone may or may notbe diseased or adversely affected. Healthy cancellous bone can besacrificed by significant compaction to improve the delivery of a drugor growth factor which has an important therapeutic purpose. In thisapplication, the size of the expandable structure 56 is chosen by thedesired amount of therapeutic substance sought to be delivered.

It should be understood that the filling material 88 itself could beused to expand the structure 56 within the vertebral body 26, therebycausing compaction of the cancellous bone 32 and/or movement of thecortical bone 28 as previously described. If desired, the fillingmaterial 88 within the structure 56 could be allowed to harden, and thestructure 56 and hardened filling material 88 could remain within thevertebral body 26. This would significantly reduce the possibility ofnon-hardened filling material 88 leaking outside of the vertebral body26. Alternatively, the pressurized fluid could be withdrawn from thestructure 56 after formation of some or all of the cavity 80, and fillermaterial 88 could be injected into the structure to fill the cavity 80and/or complete expansion of the structure 56. As another alternative,filler material 88 could be used to expand the structure 56, and thestructure 56 could subsequently be removed from the vertebral body 26before the filling material 88 within the vertebral body 26 sets to ahardened condition. If desired, the structure 56 can be made from aninert, durable, non-degradable plastic material, e.g., polyethylene andother polymers. Alternatively, the structure 56 can be made from abio-absorbable material, which degrades over time for absorption orremoval by the body. As another alternative, the filling material couldcomprise a two-part material including, but not limited to, settablepolymers or calcium alginate. If desired, one part of the fillingmaterial could be utilized as the expansion medium, and the second partadded after the desired cavity size is achieved.

The structure can also be made from a permeable, semi-permeable, orporous material, which allows the transfer of filling material and/ormedication contained in the filling material into contact withcancellous bone through the wall of the structure. If desired, thematerial can comprise a membrane that allows osmotic and/or particulatetransfer through the material, or the material can comprise a materialthat allows the medication to absorb into and/or diffuse through thematerial. Alternatively, medication can be transported through a porouswall material by creating a pressure differential across the wall of thestructure. As another alternative, fluids, cells and/or other materialsfrom the patient's body can pass and/or be drawn through the materialinto the structure for various purposes including, but not limited to,bone ingrowth, fluid/cellular analysis, bone marrow harvesting, and/orgene therapy (including gene replacement therapy).

The features of the invention are set forth in the following claims.

1. A system for treating bone comprising a first tool establishing apercutaneous access path to a bone structure having cortical boneenclosing a cancellous bone volume, a second tool comprising a structurehaving a distal end and being sized and configured to be inserted intothe bone structure through the percutaneous access path, a mechanismcoupled to the structure operable (i) to move the structure to a wrappedcondition prior to passage and withdrawal of the structure through thepercutaneous access path, and (ii) to expand the structure to anexpanded condition to form a cavity in the cancellous bone volume, themechanism comprising a catheter member extending through the structureand having a distal end anchored to the distal end of the structure, anda stylet extending through the catheter member and having a distal endfixedly and nonremovably secured to the distal end of the cathetermember, the stylet being twistable to selectively wrap the structureonto, and unwrap the structure from, the catheter member, and a thirdtool to convey a filler material into the cavity.
 2. A system accordingto claim 1 wherein the structure is adapted to compact cancellous boneupon expansion.
 3. A system according to claim 1 wherein the fillermaterial comprises bone cement.
 4. A system according to claim 1 whereinthe filler material comprises synthetic bone substitute.
 5. A systemaccording to claim 1 wherein the filler material comprises a flowablematerial that sets to a hardened condition.
 6. A system for treatingbone comprising a first tool establishing a percutaneous access path toa bone structure having cortical bone enclosing a cancellous bonevolume, a second tool comprising a structure having a distal end andbeing sized and configured to be inserted into the bone structurethrough the percutaneous access path, a mechanism coupled to thestructure operable (i) to move the structure to a wrapped conditionprior to passage and withdrawal of the structure through thepercutaneous access path, and (ii) to expand the structure to anexpanded condition within the cancellous bone volume to move fracturedcortical bone, the mechanism comprising a catheter member extendingthrough the structure and having a distal end anchored to the distal endof the structure, and a stylet extending through the catheter member andhaving a distal end fixedly and nonremovably secured to the distal endof the catheter member, the stylet being twistable to selectively rotatethe catheter member and wrap the structure onto, and unwrap thestructure from, the catheter member, and a third tool to convey a fillermaterial into the cancellous bone volume.
 7. A system according to claim6 wherein the structure is adapted to compact cancellous bone uponexpansion.
 8. A system according to claim 6 wherein the filler materialcomprises synthetic bone substitute.
 9. A system according to claim 6wherein the filler material comprises a flowable material that sets to ahardened condition.
 10. A system according to claim 6 wherein expansionof the structure forms a cavity in cancellous bone.
 11. A systemaccording to claim 6 wherein the filler material comprises bone cement.12. A method for treating bone comprising: establishing a percutaneousaccess path to a bone structure having cortical bone enclosing acancellous bone volume, deploying a structure into the cancellous bonevolume through the percutaneous access path, the structure having adistal end, with a catheter member extending through the structure andhaving a distal end anchored to the distal end of the structure, and astylet extending through the catheter member and having a distal endfixedly and nonremovably secured to the distal end of the cathetermember, moving the structure to a wrapped condition by twisting thestylet to rotate the catheter member and wrap the structure onto thecatheter member, expanding the structure to an expanded condition toform a cavity in the cancellous bone volume, and conveying a fillermaterial into the cavity.
 13. A method according to claim 12 furtherincluding, after the expanding, moving the structure to a wrappedcondition, and withdrawing the structure, while in a wrapped condition,from the cancellous bone volume through the percutaneous access path.14. A method according to claim 12 wherein expansion of the structurecompacts cancellous bone.
 15. A method according to claim 12 wherein thefiller material comprises bone cement.
 16. A method according to claim12 wherein the filler material comprises synthetic bone substitute. 17.A method according to claim 12 wherein the filler material comprises aflowable material that sets to a hardened condition.
 18. A method fortreating bone comprising: establishing a percutaneous access path to abone structure having cortical bone enclosing a cancellous bone volume,deploying a structure into the cancellous bone volume through thepercutaneous access path, the structure having a distal end, with acatheter member extending through the structure and having a distal endanchored to the distal end of the structure, and a stylet extendingthrough the catheter member and having a distal end fixedly andnonremovably secured to the distal end of the catheter member, movingthe structure to a wrapped condition by twisting the stylet to rotatethe catheter member and wrap the structure onto the catheter member,expanding the structure to an expanded condition to move fracturedcortical bone, and conveying a filler material into the cancellous bonevolume.
 19. A method according to claim 18 further including, after theexpanding, moving the structure to a wrapped condition, and withdrawingthe structure, while in a wrapped condition, from the cancellous bonevolume through the percutaneous access path.
 20. A method according toclaim 18 wherein expansion of the structure compacts cancellous bone.21. A method according to claim 18 wherein expansion of the structureforms a cavity in cancellous bone.
 22. A method according to claim 18wherein the filler material comprises bone cement.
 23. A methodaccording to claim 18 wherein the filler material comprises syntheticbone substitute.
 24. A method according to claim 18 wherein the fillermaterial comprises a flowable material that sets to a hardenedcondition.